/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.facebook.presto.execution;

import com.facebook.presto.Session;
import com.facebook.presto.adaptive.AdaptiveMetadataManager;
import com.facebook.presto.adaptive.AdaptiveUtil;
import com.facebook.presto.metadata.Metadata;
import com.facebook.presto.metadata.QualifiedObjectName;
import com.facebook.presto.security.AccessControl;
import com.facebook.presto.spi.TableHandle;
import com.facebook.presto.spi.adaptive.metadata.presto.PrestoTable;
import com.facebook.presto.sql.analyzer.SemanticException;
import com.facebook.presto.sql.tree.DropTable;
import com.facebook.presto.sql.tree.Expression;
import com.facebook.presto.transaction.TransactionManager;
import com.google.common.collect.Lists;
import com.google.common.util.concurrent.ListenableFuture;

import java.util.List;
import java.util.Optional;

import static com.facebook.presto.metadata.MetadataUtil.createQualifiedObjectName;
import static com.facebook.presto.sql.analyzer.SemanticErrorCode.MISSING_TABLE;
import static com.google.common.util.concurrent.Futures.immediateFuture;

public class DropTableTask
        implements DataDefinitionTask<DropTable>
{
    @Override
    public String getName()
    {
        return "DROP TABLE";
    }

    @Override
    public ListenableFuture<?> execute(DropTable statement, TransactionManager transactionManager, Metadata metadata, AccessControl accessControl, QueryStateMachine stateMachine, List<Expression> parameters)
    {
        AdaptiveMetadataManager adaptiveMetadataManager = AdaptiveUtil.getMetadataManager();

        // adaptive module
        if (adaptiveMetadataManager.isAdaptEnable()) {

            // get all catalogs by name.
            List<PrestoTable> allPrestoTables = getPrestoTablesByName(statement);

            // loop to drop table in these catalogs.
            for (PrestoTable prestoTable : allPrestoTables) {
                // create table in engine.
                QualifiedObjectName tableName = new QualifiedObjectName(prestoTable.getCatalog(),
                        prestoTable.getSchema(),
                        prestoTable.getTable());
                internalExecute(statement, tableName, metadata, accessControl, stateMachine.getSession());

                // drop table in presto-metadata.
                adaptiveMetadataManager.removeATable(tableName.getCatalogName(), tableName.getSchemaName(), tableName.getObjectName());
            }
            return immediateFuture(null);
        }
        // normal module.
        else {
            QualifiedObjectName tableName = createQualifiedObjectName(stateMachine.getSession(), statement, statement.getTableName());
            return internalExecute(statement, tableName, metadata, accessControl, stateMachine.getSession());
        }
    }

    private ListenableFuture<?> internalExecute(DropTable statement,
            QualifiedObjectName tableName,
            Metadata metadata,
            AccessControl accessControl,
            Session session)
    {
        Optional<TableHandle> tableHandle = metadata.getTableHandle(session, tableName);
        if (!tableHandle.isPresent()) {
            if (!statement.isExists()) {
                throw new SemanticException(MISSING_TABLE, statement, "Table '%s' does not exist", tableName);
            }
            return immediateFuture(null);
        }

        accessControl.checkCanDropTable(session.getRequiredTransactionId(), session.getIdentity(), tableName);

        metadata.dropTable(session, tableHandle.get());

        return immediateFuture(null);
    }

    /**
     * Get presto tables by table name.
     */
    private List<PrestoTable> getPrestoTablesByName(DropTable statement)
    {
        // adaptive module.
        String tableName = Lists.reverse(statement.getTableName().getParts()).get(0);

        AdaptiveMetadataManager adaptiveMetadataManager = AdaptiveUtil.getMetadataManager();

        List<PrestoTable> tableExisting = adaptiveMetadataManager.getPrestoTablesByTableName(tableName);

        if (tableExisting == null || tableExisting.isEmpty()) {
            throw new SemanticException(MISSING_TABLE, statement, "Table '%s' does not exist", tableName);
        }

        return tableExisting;
    }
}
